Floating toolholder



T. w. FLORY- 2,671,667

FLoA'rING 'TooLHoLDER v 2 sheets-sheet 1 /Horney March 9, 1954 FiledFeb. 8, 1951 Mrch 9, 1954 T. W, FLORY 2,671,667

FLOATING TOOL-HOLDER Filed Feb. 8. 1951 2 Sheets-Sheet 2 /nven75r YTHOMAS W/Qss FLoRy AWO/wey Patented Mar. 9, 1954 UNITED affair-151sPATENT oFFICE FLoA'rING TooLHoLDEa Thomas Wass Flory, lliolkestone,England Appunti@ February s, 1951, serial No. 210,073

v (o1. 27s-1s) 16 Claims.

g 1 g e This invention relates to iioating tool holders, of the kind inwhich the tool is held and rotated about its longitudinal axis, but isarranged to be permitted a small displacement Afrom said axis duringrotation, and especially, but not exclusively, of the kind in which thetool is operated through a guide or series of guides designed tocentralize said tool in relation to the workpiece, such guide beingpreferably incorporated in the tool holder housingitselfr.Alternatively, tool holders of the type tobe described may 'be `used tooperate toolsv through separate guides, or for reaming or opening outexisting holes, or for any vapplication where the tool is tending tovfollow a predetermined path.

It is known to provide a chuck for a drill in which the drive istransmitted through a series of grooved plates, steelballs being locatedin the grooves andallowing the plates to be displaced laterallyrelatively toone another, Yso that the drill can rotate-about an axisparallel with the axis of rotation of the chuck.,

An object of the present invention, however, is to provide a holder fora tool, such as a drill, which may not only be operated on an axisparallel to that of the drill spindle but'which will carry the tool insuch a Way that undesirable stresses on the tool, such as lateralstresses caused by misalignment of the tool'on a curved surface of thework to be machined, are minimised. In the latter case the displacementof the axis of the tool fromthe axis ofthe chuck may be regarded,therefore, as an angular displacement about an intermediate nodal pointon'the axis of the chuck. This nodal point may itself,V

however, be slightly offset from the axis of the chuck.

A further object of the invention is to provide means whereby the toolcan be displaced laterally with respect to the axis of rotation of thetool holder, or can take up a position at a slight angle to the saidaxis, with greater ease and less risk of the parts jamming or bindingthan in previous chucks.

According to the invention a holder for a rotary tool, for mounting in.a machine tool, is provided with a driving member arranged to besecured to the machine, va driven member rotated by Said driving memberand so supported bythe driving member as to be free to float to alimited extent in any direction radially with respect to the axis ofrotation of the driving member, and, means for securinga toolto thedriven member, the driving and driven members constituting a kinematicpair of elements.

It is to be understood that theterm kinematic pair of elements usedherein is intended to de-y ne two bodies constrained to maintain contact(with or without an intervening anti-frictiondevice not otherwiseaffecting the operation 4of the pair) while relative Amovement .takesplace between them. l

The holder may be arranged to accommodate a drill or reamer that is totake a pathpredetermined by a center hole onthe onehand or `a hole to bereamed out on the other, the ,floating driven member enabling the end`of the tool to` locate the center or hole andthen to operate, ifnecessary, oiA center, either parallel to or at a limited angle with thesaid axis. Alternatively, the holder may be provided with a tool guidewhich engages the work at one end and is supported by the driving memberat the other, the

floating driven member in lthis arrangement serving to relieve frictionin the guide when there is a tendency for the tool point to be forcedoff center.

Advantageously, the said driven member may include a drum mounted with acomparatively small circumferential clearance in a socket provided inthe driving member, the drive between the two members being eilected byat least one projectionengaging a recess having such clearance withrespect to the projection as to permit theA drum to float radially.

In order that'the invention may be clearlyI understood and readilycarried into effect, some constructions in accordance therewith will nowbe described, by way of example, with referenceto the accompanyingdrawings, in which:

Figure 1 is a sectional elevation of one form of tool holder, shownholding a twist drill;Y

Figure y2 is a section on the line II-'II in' Figure 1;

Figures 3 and 4 are a plan and front end elevation respectively of theforward portion of the The body or driving'member I consists of a hol--low tapered spigotA 2, closed at the smaller end except for a smallApassage 3, and at the larger end formed as a cylindrical open-endedsocket 4 of considerably greater diameter than the spigot.

The open end of the socket is internally threaded to receive acorrespondingly threaded end `5 of an open-ended sleeve 6 forming anextension of the socket, the inner end of said sleeve forming aninwardly projecting shoulder within the socket 4. The sleeve '6 may beconsidered as part of the socket 4.

Between this shoulder 'I and that end of the socket adjacent to thespigot, which will be termed the closed end, there is disposed a drum 8,consisting of a cylindrical block of metal or other suitable materialslightly smaller in diameter than the bore of the socket, so that it ispermitted radial float therein. The shoulder of the sleeve and theclosed end of the socket limit the axial movement of the drum within thesocket. At the transverse plane of contact between said closed end andthe drum there are four passages 9 parallel to the axis of the drum andspaced equally around the periphery. Each passage accommodates a pin I4,carried by the socket 4, which is loose enough, relatively to the drum,to allow said drum to move radially within the limits prescribed by itsfloat in the socket.

At its outer end the drum 8 is recessed to accommodate a thrust race I5against which lbears one end of a helical compression spring I0. Theother end of this spring bears against a shoulder II in aV drill `guidein the form of a sleeve which is mounted rotatably and slidably within abush |2 carried by the sleeve 6, and is formed at its outer end withdivergent horns I3. Complete ejection of the tool guide I1 is preventedby a split ring 3| mounted in a recess in the tail end ofthe tool guideI'I and arranged to engage the end of the bush I2.

The twist drill I8 is xed to one end of a drill holder I9 clamped in apassage 20 in the drum 8 by an Allen or set screw 2| that is screwedinto a radial passage '22 in the drum 8 and bears on a lateral surface23 on the drill holder I9. rIhe surface 23 is recessed and slightlyinclined to the axis of the drum sow-as to prevent the tool fromslipping axially relatively thereto when the set screw has been adjustedand pressure is exerted between the tool and the work. The surface 23 isalso grooved and limited in length to prevent the tool from turningabout its axis with respect to the drum and from being completelyejected by spring 32 when the setscrew 2| is released. The drill issupported in the drill guide I'I by an interchangeable bush 24 screwedinto the guide at 25 and locked lby a set screw 26 carried by the guideI1 and engaging a groove in the outer surface of the bush 24. The bush24 is formed with radial passages 2l and the drill `guide Il with radialpassages 28 for the disposal of swarf. If desired the bush 24 may beformed with an internal groove joining the passages 21 to receive theswarf. Y

Each of the set screws 2| and 26 is formed with a hexagonal-sectionrecess to receive a correspondingly shaped Allen key. Access to the setscrew 2| is obtained through an aperture 29 in the wall of the socket 4.To balance the drum 8 a recess 30 is formed therein diametricallyopposite the set-screw 2|. It will be observed that, as the set screw 2|does not project outside the socket 4, it presents no danger in use.Moreover, as the aperture 29 is of smaller diameter than the set screw2|, the latter cannot be removed without dismantling the assembly. Theinternal diameter of the socket 4 is such that the set screw 2| can bewithdrawn sufficiently to permit the drill to move longitudinally adistance corresponding to the length of the groove surface 23, althoughthe hemispherical end 2|a cannot be withdrawn so much as to permit it toescape from the groove surface 23'.

The hollow spigot 2 accommodates a compression spring 32 which bears ona pad 33, slidable within the hollow interior, and urges it outward fromthe spigot. This pad 33 in turn bears on the inner end of the drillholder I9. Ejection of the pad 33 from the spigot '2 is prevented by aretaining collar 34 screwed into the closed end of the socket 4.Moreover, the drill holder I9 cannot be shot forward further than ispermitted by the engagement of the left hand end of the surface 23 withthe end 2| a of the set screw 2|. An oil hole 35a as well as theaperture 29 prevents air pressure from building up behind the tool guidewhen the latter moves inwards.

From the foregoing it will be seen that, generally speaking whenthedrill is now fed down on to the work, with the machine running, theguide |I remains stationary straddling the work, sleeve 6 and bush l2rotating on the guide as on a journal. As the drill continues to be feddownwardly, the socket 4 descends relatively to the `guide against thecompression spring I 0. Rotary motion of the socket is imparted to thedrum through the four radial pins I4, and so to the drill |8. Lateralstresses on the drill, due to inequalities in the work or other causes,may result in the drill becoming slightly offset relatively to the axisof the holder. The upper end of the drill, where it passes through thedrum, may be offset in the direction opposite to that of the lateralstress on the drill to the extent, on the one hand, of the radial floatpermitted to the drum B, and, on the other hand, of the small tolerancebetween the bush I2 and the guide I'I and the bush 24 and the drill 8.The nodal point, that is, the intersection of the axes of the drill andthe tool holder, is within the bore of the drill guide.

in this way there is obviated the fracture of drills due to bendingunder lateral stress, and a more accurate and rapid drilling,particularly of transverse holes in rods and bars, may be achieved.

To set the drill initially, release the set screw 2| permitting thedrill I 8 in holder I9 to be forced outwards by the action of the spring32 until the end 2|al of the set screw 2| occupies the extreme positionM remote from the drill point, in the groove 23. The drill point willthen protrude beyond the extremity of the drill guide to approximatelythe position J.

Now place the tool in a drill press and bring it down towards theworkpiece W which will rst be contacted by the drill point and then (asvdownward movement continues, and the drill I8 is forced backwardsagainst the spring 32) by the horns |3. As pressure is continued stillfurther, the drill guide I1 compresses the spring ID so that the hornsare now firmly held against the workpiece W. Pressure should be furthercontinued until the selected annular index mark 35 is in line with theouter edge of the bush I'2 when the drill holder I9 should be locked bymeans of set screw 2| which will then be located somewhere between thetwo extremities of the groove 23. The drill point will then be in theposition K. The annular index mark 35 to be selected will depend on thesize of drill in use, greater compression of spring I0 being desirablefor the larger drills. The tool is then retracted from the work allowingthe tool guide |'I to be forced outwards Iby spring it in. relationtothe drill point;l For examplerit maybe retractedk to the L; Thus-Whenthe toolfis applied. to the worin. thexhornsxt' straddle the workpieceunder `considerable pressure trom thek spring' I- and before Vcontact ismade by the drill point. This ensures'that ther drill' is' properly andaccurately applied to the work.YY Y

. It isi'to be noted that the maximum deptlrrof manner', withoutdismantling the apparatus.

' Having drilled. to the maximum possible'depth on. therst applicationor the tool,;.raise the drill press, thus withdrawing thezdrill from'the bored hole, keeping the horns t3 still Aincontact with theworkpiece. Then release the set screw/2| whereupon the spring 32 forcesthe'drill outwards until it is checked `by the extremity M of the groove23 or the bottom of the :hole already drilled. Then tighten set screw 2|to grip. the drill holder in its new position. By a further operation ofthe drill press a `correspondingly deeper' hole may then be drilled inthe workpiece. For example, if at the rst drilling the set screw 2| isat position N, then themaximum additional depth. obtainable at thesecond drilling is the length M-Nequivalent to amo-vement J-P or' thedriil point. Y

The construction shown Yin Figures 5 and 6 differs from thatparticularly described above mainly in the shape of thevdrill guide, theman-A ner of mountingthe drill guide and the manner in which the drum isdriven. It will be seen that the tool guide 38 is formed with a,frusto-conical recess 31 Yfor engaging a'frustmconical end on aworkpiece and with a skirt 3a fixed in one end of. a sleeve 39 carryinga bush 40 reciprocable on the outside of the body 4| of the tool holder.The guide 36 is urgedoutwards by a spring 42 and the forward movement islimited by van annular cap 43`screwed into the sleeve 39 and bearing ona shoulder on the body 4|. The centre drill 4'5 is mounted in preciselythe same'way as the drill holder in the construction. of'Figures l to 5but the drum 46 is driven by two radial pins '41 that project with someclearance into apertures. 48 in the cylindrical wall of the socket 49 ofthe body 4|. As in the construction of Figure 1, the socket 4| is formedwith an aperture 50 giving access to the set-screw 2 la, and apertures5| are provided for the same purpose in the sleeve 39 and lbush 40.These apertures 5| only register with the aperture 50 when the toolguide hasbeen pressed back far enough and the parts turned relatively toone another suiiiciently to bring the apertures into axial alignment.Markings'respectively on the part 52 of the body 4| and on the assemblycomprising the sleeve 39 and ycap 43 indicate when the apertures are inalignment.Y

In the construction shown in Figures 5 and y6 the radial clearancebetween thelsocket. 49 andV the drum 46, when the latter is centred, isve one thousandths of an inch.

Operation is substantially similar to that of the previous embodiment.'Owing tothe presence, however, of the outer sleeve 39 which forms partof the guide, the guide may be brought to rest while the toolholder'isrotating, merely by the operator gripping the guide. This eliminatesdamage to a delicate workpiece through frictional contact with arevolving guide. The embodiment is limited to workpieces of regularshape,

that is, balls or knobs, the ends o! bars, bosses, or the like ofcircular cross-section,or of regular triangular, square, or polygonalcross-section. Such a workpiece is centredv by the guide as hasexplained in connection with the previous embodiment.

l'. claim:

l. A. holder for a rotary tool,v for mounting in a machine tool, saidholder comprising, in combination, a driving member arranged to besecured to the machine to rotate about an axis, a driven membersupported by and operatively connected to said driving member so'as tobe driven thereby while free to float to a' limited extent in anydi,

rection radially with respect to they axis of rotation of said drivingmember, means for securing a tool to said drivenmember to rotate aboutsaid axis, a tubular tool guide coaxial Vwith said driving member andmounted to reciprocate thereon while being free to'remain stationaryassaid member rotates, and resilient mean-s urging said guide towardsthe Work to be machined, said guide being formed at its outer end toengage the work and so'be steadied thereby.

2. A holder according to claim l, in which said tool guide is formed atits outer end with divergent horns arranged to straddle a round bar withits axisA at right angles to the tool.

3. A holder'accordng to claim 1, in which said tool guide is formed atits outer end with a conical recess arranged to engage the work formedwith a conical end.

4. A holder according toclaim l, in which the tool guide is formed withan aperture between its ends for the 'disposal of swart'.

5. A holder according to claim l, in which said tool guide and saiddriving member are formed with marks adapted to indicate when said toolguide has been pressed backwards a predetermined distance against saidresilient means, and in which said means for securing' the tool to saiddriven member are operable when said guide is thus pressed backwards.

6. A holder according to claim l, provided with resilient means forurging the tool outwards from said driven member, and the said means forsecuring the tool to said driven member being adapted to enable saidtool to be secured to said Y driven member after said tool and saidguide 'loY have simultaneously been pressed backwards against theirrespective resilient means to a pre determined extent, while said guideis left free to be projected forwards again, relatively to the tool,under the action of the resilient means associatedr with said guide.

T. A holder for a rotary tool, for mounting in a machine tool, saidholder comprising, in combination, a driving member arranged to besecured to the machine to rotate about 'an axis and formed with a socketconcentric with said axis, a tubular tool guide coaxial with saiddriving member and mounted toreciprocate thereon while being free toremain stationary as said member rotates, a driven member mounted insaid socket and operatively connected to said driving member so as to bedriven thereby while free to float in any direction radially withrespect to said axis, means for fixing to said driven member a toolfitting inside said tubular tool guide, and resilient means urging saidguidetowards the work to be machined, said guide being formed at itsouter end to engage the work and so be steadied thereby.

8. A holder according to claim 7, in which said resilient means isconstituted by a compression spring, said holder being further providedwith 7. an anti-friction bearing which together with said spring isinterposed between said driven member and said guide.

9. A tool assembly comprising a rotary tool having a shank formed on oneside with a surface inclined to the axis of said tool and a holder forsaid tool, for mounting in a machine tool said holder comprising, incombination, a driving member arranged to be secured at one end to amachine, to be rotated thereby, and formed with a socket and furtherformed with a lateral passage leading into said socket, a driven membermounted with a comparatively small circumferential clearance in saidsocket, said driven member being formed with an axial passage to receivea tool and with a lateral screw threaded passage, a set screw in saidthreaded passage for securing said tool in said driven member byengaging said inclined surface so as to prevent the tool from slippingaxially and circumferentially when applied to the work, said set screwbeing wholly within said socket and of such diameter that it cannot beremoved through said lateral passage but being adapted to be screwed toa limited extent through said threaded passage by means inserted throughsaid lateral passage, and means operatively connecting said driving anddriven members so that said driven member is rotated by said drivingmember while being free to undergo translational floating movementradially relatively thereto.

10. A holder for a rotary tool, for mounting in a machine tool, saidholder comprising, in combination, a driving member arranged to besecured to the machine to rotate about an axis, means for securing adriving connection between a tool and said driving member so as to causethe tool to rotate with said driving member, a tubular tool guidecoaxial with said driving member and mounted to reciprocate thereonwhile being free to remain stationary as said member rotates, rstresilient means urging said guide towards the work to be machined, saidguide being formed at its outer end to engage the work and second so tobe steadied thereby, and resilient means for urging the tool outwardsfrom said driving member, said means for securing said drivingconnection between the tool and said driving mem ber being adapted toenable said connection to be made after the tool and said guide havesimultaneously been pressed backwards against their respective resilientmeans to a predetermined extent, whereby said first resilient meansmaintains the guide iirmly against the work throughout the drillingstroke of said tool and said second resilient means serves to force thetool forward when said securing means is released thereby enabling saidtool to be locked in a new position relatively to said driving member.

11. A holder for a rotary tool as claimed in claim 10, in which theouter end of the guide is formed with divergent horns arranged tostraddle a round bar with its axis at right angles to the tool.

12. A holder for a rotary tool as claimed in claim in which the outerend of the tool guide is formed with a conical recess arranged to engagethe work formed with the conical end.

13. A holder for a rotary tool as claimed in claim 10, in which the toolguide is formed with an aperture between its ends for the disposal ofswarf.

14. A holder for a rotary tool, for mounting'in a machine tool, saidholder comprising, in combination, a driving member arranged to be secured to the machine to rotate about an axis, means for securing a toolto said driving member to rotate about said axis, a tubular tool guidecoaxial with said driving member and mounted to reciprocate thereonwhile being free to remain stationary as said member rotates, resilientmeans urging said guide towards the work to be machined, said guidebeing formed at its outer end to engage the work and so be steadiedthereby, second resilient means being mounted in said driving member andbeing adapted to exert an axial thrust on the tool when the latter ismoved in a direction away from the work engaging end of the tool guide,so that the tool may be lockedy by said securing means to said drivenmember with said second resilient means stressed, and an anti-frictionthrust bearing interposed between said iirst-mentioned resilient meansand said driven member.

15. A tool assembly according to claim 9, wherein said surface on saidshank is provided with a longitudinal groove and wherein the inner endof said set-screw projects into said groove in all positions ofadjustment thereof, whereby said set screw remains in register with saidgroove during the longitudinal adjustment ofthe tool with respect tosaid driven'member.

16. A holder for a rotary tool, for mounting in a tubular driving memberarranged to be secured to the machine to rotate about an axis, a drivenmember mounted within said driving member and formed with an axialpassage to receive a tool shank, a driving connection between said twomembers whereby said driven member is rotated by said driving memberwhile being free to undergo translational floating movement radiallyrelatively thereto, a tubular tool guide telescopically mounted withinsaid driving member and projecting from one end of the latter, said toolguide being free to remain stationary while said driving and drivenmembers rotate and being formed at its outer end to engage the work andso be steadied thereby, a compression spring interposed between saiddriven member and said tool guide, an anti-friction thrust bearinginterposed between said spring and said driven member, a secondcompression spring, said springs being coaxial with the tool guide andsaid second compression spring being adapted to act at one end on saiddriving member and at the opposite end on the inner end of the toolshank, and means for locking the shank to said driven member.

THOMAS WASS FLORY.

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